The present invention relates to treating aqueous polymer solutions used in polymer floods of subterranean formations to enhance the recovery of oil.
The fundamentals of enhanced oil recovery polymer flooding of subterranean formations are well known to those skilled in the art. See, for example, H.K. van Poollen and Associates, Inc., Fundamentals of Enhanced Oil Recovery, PennWell Publishing Co., Tulsa, OK (1980), chapter 5 (van Poollen). Generally, in a polymer flood, a polymer is added to water to form a viscous polymer solution. When the polymer solution is injected into an oil reservoir, the oil is more efficiently recovered from the formation. The polymer solutions must be matched with characteristics (e.g., pore size distribution, permeability, and salinity) of the subterranean formation to achieve optimum results and to prevent formation damage.
Shearing the polymer solution is one method for optimizing polymer solution properties. The advantages of selectively shearing solutions of partially hydrolyzed polyacrylamide are noted in published British patent application 2,001,999 (Grodde). Grodde employs perforated plates to achieve his desired degree of shearing. Another polymer flood system employing plates to shear the polymer is discussed and illustrated in Dovan et al., SPE 20060 (1990) (Dovan), this paper being incorporated herein in its entirety by reference.